Exploring the photoleakage current and photoinduced negative bias instability in amorphous InGaZnO thin-film transistors with various active layer thicknesses

Abstract

The photoleakage current and the negative bias and illumination stress (NBIS)-induced instability in amorphous InGaZnO thin-film transistors (a-IGZO TFTs) with various active layer thicknesses (TIGZO) were investigated. The photoleakage current was found to gradually increase in a-IGZO TFTs irrespective of the TIGZO when the photon energy of visible light irradiation exceeded ≈2.7 eV. Furthermore, the influence of the TIGZO on NBIS-induced instability in a-IGZO TFTs was explored by the combination of current–voltage measurements in double-sweeping VGS mode and capacitance–voltage measurements. The NBIS-induced hysteresis was quantitatively analyzed using a positive gate pulse mode. When the TIGZO was close to the Debye length, the trapped electrons at the etch-stopper/IGZO interface, the trapped holes at the IGZO/gate insulator interface, and the generation of donor-like states in an a-IGZO layer were especially prominent during NBIS.

Keywords

• active layer thickness
• gate bias
• illumination stress
• InGaZnO
• photoleakage current
• thin-film transistors